June, 1923 | HARVEY — MALTOSE IN APPLE TISSUE? 289 
Darwin and Acton, 2 and is based on the fact that maltose is not hydrolyzed 
by the regular sucrose-inversion procedure, but requires a more severe acid 
treatment, so that, after regular inversion, the solution is subjected to 
another hydrolysis with 2-percent hydrochloric acid for three hours. The 
increased reducing power of the solution after this treatment is assumed 
to be due to the splitting up of maltose. This latter hydrolytic treatment 
has been called “complete inversion,” and as such it will be referred to 
throughout this paper. The increased reducing power after “complete 
inversion” is multiplied by the factor 2.32 to give the quantity of maltose 
originally present. The method has received severe criticism from David 
and Daish, 3 but the writer immediately questioned the use of this method 
in the analysis of apple tissue for an additional reason, namely, that the 
bark of all parts of an apple tree contains considerable quantities of the 
glucoside phloridzin, which might be hydrolyzed by the “complete-in¬ 
version” treatment. If so, glucose from phloridzin would then increase the 
reducing power of the solution as though it were from maltose. Since it 
was suspected that the quantity of phloridzin might be as much as 1 or 2 
percent in apple tissue, any figures for maltose based on this method seemed 
open to serious criticism. 
Toward an understanding of the relations between maltose and phloridzin 
in apple tissue, the following considerations and tests were made: 
Qualitative Considerations. In chemical literature phloridzin has 
frequently been reported as a normal constituent of apple tissue, and the 
writer himself has repeatedly isolated and prepared pure crystalline 
phloridzin from spurs and shoots of apple trees. It is always possible to 
obtain a positive test for phloridzin in apple bark by means of such reagents 
as ferric chloride, mercuric nitrate, or strong sulphuric acid, while it is 
quite impossible to secure a positive test for maltose in similar tissue by 
such reagents as phenylhydrazine. 
Behavior of Pure Phloridzin under the “ Complete-Inversion ” Treatment. 
To determine the extent to which phloridzin is affected by the methods 
of sugar analysis, 2.426 grams of crystalline phloridzin (equivalent to 2.24 
grams anhydrous phloridzin) were dissolved in water, and the volume was 
made up to 1000 cubic centimeters. Portions were carried through the 
regular procedures for (a) “direct-reducing” sugars; ( h ) “total sugars after 
inversion”; and (c) “complete inversion.” In each case the amount of 
solution submitted to the reduction procedure contained 0.083 gram of 
anhydrous phloridzin, which on complete hydrolysis should yield 34.2 
milligrams of glucose, according to the accepted formula for phloridzin: 
C21H24O10 + H2O = CeHi 2 06 + C15H14O5 
Phloridzin Glucose Phloretin 
2 Darwin and Acton. Practical physiology of plants, p. 285. 1901 (reprint, 1909). 
3 David, W. A., and Daish, A. J. A study of the methods of estimation of carbo¬ 
hydrates, especially in plant extracts. Jour. Agr. Sci. 5: 437-468. 1913. 
